1. Field of the Invention
The invention generally relates to an optical module, and more particularly to a light source module.
2. Description of Related Art
In the prior art, a light source module used for a vehicle headlight may be roughly divided into reflective one and projective one. In the application of the headlights, the reflective light source module requires to employ a large reflective cover to converge the beam effect, so that the reflective light source module has a larger volume. In particular, the light-radiation pattern of the reflective light source module at the front of the vehicle with 25 meters distance tends having problem of indistinct bright-dark cut-off lines. In addition, since the light beam in the module is reflected by the reflective cover, the reflective light source module has a poor light utilization efficiency. The projective light source module, on the contrary, is able to form a light-radiation pattern with distinct bright-dark cut-off lines at the front of the vehicle with 25 meters distance by employing a light barrier. However, the light barrier would block some of light beam to exit and thereby affect the light utilization efficiency of the projective light source module. In addition, how to achieve the configuration of light-radiation pattern of ECE R112 code in Regulations of United Nations Economic Commission for Europe (ECE regulations) is still a big challenge for the projective light source module. In general speaking, in order to form an uniform bright surface, the luminance of bright spots are usually not sufficient or it fails to form bright spots at predetermined positions and the bright-dark cut-off lines between bright surface and dark surface are indistinct as well. If the luminance of bright spots is enough, the uniformity of bright surface is not satisfied or the light-radiation pattern of bright surface does not conform with a predetermined shape. For a conventional illumination or projection system, the bright spot is usually located at its middle; if the bright spot needs to be close to the edge of a bright surface by design, complicated optical elements are required, and employing so complicated optical elements, in turn, would reduce the luminance of the bright surface so that a larger power of the light source is needed.
U.S. Pat. No. 5,581,683 discloses a scheme that the light beam emitted by a light-emitting diode (LED) passes through a U-shape light-guiding device to reach at a light diffuser. U.S. Pat. No. 7,581,862 discloses another scheme that the light beam emitted by an LED reaches at a focusing lens via a ring-shape light-guiding device. U.S. Pat. No. 7,980,741 discloses yet another scheme that a light beam produced by a light source of a vehicle headlight reaches at a light emitting surface of a light-guiding structure via the light-guiding structure. Taiwan patent application publication No. 200912200 discloses a scheme that a radial optical signal emitted by a light source produces a collimated signal parallel to the exiting light through a transmission device and a collimator device (i.e. a direction-turning device). Taiwan patent application publication No. 200639518 discloses an illumination system including a plurality of collimating segments and a light-mixing segment. U.S. Pat. No. 5,757,557 discloses a conic lens with planes and internal cavities. U.S. Pat. No. 7,401,947 discloses an optical device for the light beam emitted by a light source to pass through and an optical equipment.